The present invention generally relates to rotary recording medium reproducing apparatuses, and more particularly to a reproducing apparatus for reproducing a rotary recording medium alternately recorded with first and second reference signals for tracking control, on both sides of a track for every one track turn, and also recorded with a third reference signal for switching used upon reproduction when forming a tracking control signal, at a predetermined position in each track turn, and capable of accurately obtaining the tracking control signal upon reproduction of this rotary recording medium even when a noise component exists or dropout of the third reference signal occurs.
Systems have been realized in which a recording system forms pits in accordance with information signal being recorded along a spiral track on a flat rotary recording medium (hereinafter referred to as disc), without forming a groove therein, and a reproducing stylus traces over along this track to reproduce the recorded information signal in response to variations in the electrostatic capacitance in a reproducing system.
In this system, since no groove is provided on the disc for guiding the reproducing stylus, pilot or reference signals are recorded on or in the vicinity of a track of the information signal, such as a video signal, on the disc. Upon reproduction, the reference signals are reproduced together with the video signal. Tracking servo control is carried out so that the reproducing stylus accurately traces along the track in response to the reproduced reference signals.
In the above disc, only one of a first and second reference signals fp1 and fp2 is recorded at an intermediate position between center lines of adjacent track turns. Moreover, the side on which the first and second reference signals are recorded with respect to one track turn changes over every one track turn. That is, when the first and second reference signals are respectively recorded on the right and left sides of one track turn, the relationship between the recorded positions of the reference signals is such that the second and first reference signals are respectively recorded on the right and left sides of adjacent track turns. Furthermore, a third reference signal fp3 for obtaining a switching signal upon reproduction, is recorded for every track turn at recording switching positions of the above first and second reference signals.
In a reproducing apparatus, a changeover operation is performed by use of the third reference signal reproduced upon obtaining of a tracking control signal from the reproduced first and second reference signals.
Since no grooves are provided in the above disc, the reproducing stylus can be transferred from one track to another without damaging the reproducing stylus or the disc. Accordingly, in addition to the special reproduction such as still reproduction, slow-motion reproduction, and quick-motion reproduction, the system is capable of performing a so-called random access in which the reproducing stylus is transferred to a desired position at high speed to reproduce the desired information.
In the conventional reproducing apparatus, the third reference signal is simply subjected to waveform-shaping, to obtain the switching signal for switching positions of the above first and second reference signals. Hence, in a case where a noise component in the form of a pulse exists at a position other than the position where the normal third reference signal exists, or the normal third reference signal which should exist does not exist due to dropout and the like, the switching signal is not formed in a normal manner. Thus, there was a disadvantage in that the operation to switch over the first and second reference signals could not be performed in the above described case. In the above case, the tracking control signal cannot be obtained in a normal manner, and moreover, normal tracking control cannot be performed with respect to the reproducing stylus.